Imaging features of reactive bursitis secondary to osteochondroma.

PURPOSE: The purpose of this study was to determine imaging features of reactive bursitis secondary to osteochondroma. MATERIALS AND METHODS: Fourteen patients with reactive bursitis secondary to osteochondroma were retrospectively reviewed. RESULTS: The 14 patients were 11 males and 3 females ranging in age from 18 to 67 years (mean, 33.6 years). The locations were as follows: scapula (n = 2), lesser trochanter (n = 6), greater trochanter (n = 1), distal femur (n = 2), distal fibula (n = 1), iliac bone (n = 2). On CT, six bursae were hypodense and 1 was isodense compared to muscle. All bursae had a thickened wall, 6 contained multiple villous projections and septa. Five bursae contained a few calcifications. On enhanced CT, the bursa displayed mild enhancement of the wall, villous projections, and septa. On MRI, one bursa was hypointense, three were hyperintense, and 5 were isointense relative to muscles on T1-weighted images. All bursae were hyperintense relative to muscles on T2-weighted images. All bursae had a thickened wall, eight contained multiple villous projections and septa. In five bursae, a few fatty villous projections can be seen within the bursa. On enhanced MRI, all bursae displayed avid enhancement of the bursal wall, villous projections, and septa. CONCLUSIONS: Reactive bursitis secondary to osteochondroma most often occurred in young male adults. The most common involved site is lesser trochanter. The imaging features is that of an irregular, thick-walled fluid-filled bursa overlying an osteochondroma that containing multiple villous projections and septa. Calcification and/or lipoma arborescens may be developed within the bursa. On contrast-enhanced images, the bursa shows enhancement of the bursal wall, villous projections and septa.